1. Field of the Invention
This invention relates to computer system cooling and, more particularly, to fan cooling systems having redundant fan controllers and redundant fans.
2. Description of the Related Art
Computer systems are typically available in a range of configurations which may afford a user varying degrees of reliability, availability and serviceability (RAS). In some systems, reliability may be paramount. Thus, a reliable system may include features designed to prevent failures. In other systems, availability may be important and so systems may be designed to have significant fail-over capabilities in the event of a failure. Either of these types of systems may include built-in redundancies of critical components. In addition, systems may be designed with serviceability in mind. Such systems may allow fast system recovery during system failures due to component accessibility. In critical systems, such as high-end servers and some multiple processor and distributed processing systems, a combination of the above features may produce the desired RAS level.
Many systems provide redundant backup components. In a typical redundant cooling fan system, a redundant backup fan may be powered off and if the primary fan fails, the backup fan may be powered up to take over the cooling load. However in these types of systems, a primary fan controller and or a system controller must assume that the backup fan and associated control circuitry will be operational when needed.